This application claims priority to German Patent Application No. 102 24 157 0, filed May 31, 2002.
The invention relates to a drive device, in particular a cable drive for a part secured to a vehicle and to be moved relative thereto.
Drive devices, and cable drives in particular, are used to move a vehicle part (e.g., window, sliding roof, etc.) relative to a vehicle. Cable drives may comprise at least one flexible traction transfer means that is guided in the form of an endless loop and has two ends, each end having associated therewith a winding drum adapted to have the traction transfer means wound up on and unwound from it, a shared motor drive for rotating the winding drums in the same direction of rotation, and entrainment elements secured to the traction transfer means for connection with the part that is moved.
A drive device of this type for lifting and lowering a vehicle window pane is known, for example, from JP 62-15 34 80, DE 197 38 795 C1, or WO 00/35 695.
The principle of these drive devices resides in forming a pair of cable branches having parallel sections that each engage parallel lateral edges of the vehicle window and are moved up and down synchronously to avoid any tilting motion. The cable, which is guided via numerous deflection rollers, has a considerable cable length. This allows non-synchronous movements of the entrainment elements on the branches may occur, especially due to thermal expansion or wear or elongation of the cable. Although these differences in movement are very small, they may under some circumstances result in slight tilting motions or canted positions that should be avoided.
One object of the invention is to provide a drive device, in particular a cable drive for the cover of a vehicle sliding roof (including, of course, all other known types such as a folding roof, a rising roof or a sliding/tilting roof) in which the risk of non-synchronized movements of the entrainment elements is further reduced.
This object is achieved in a drive device for use in a vehicle. The drive device has at least one flexible traction transfer means that is guided in the form of an endless loop and has two ends, each end having an associated winding drum adapted to have the traction transfer means wound up on and unwound from it, a shared motor drive for rotating the winding drums in the same rotational direction, and entrainment elements secured to the traction transfer means for connection with the part that is moved.
The inventive drive device also has at least one further winding drum coupled with the drive. An intermediate section of the traction transfer means is looped around the at least one further winding drum between the ends so that at least two branches of the traction transfer means are formed between the winding drums and the further winding drum. The entrainment elements are fastened to the branches of the traction transfer means.
The further winding drum has a short, preferably central section of the traction transfer means wound up on it so that the free length of the traction transfer means, i.e., the length situated between two driven winding drums, is halved. The main reason why a synchronous driving motion is obtained using the further winding drum is because using only two winding drums causes the cable lengths between the entrainment elements and the wound-up ends to be unequal. If thermal expansion occurs, for example, this will result in a minor offset of the entrainment elements which may lead to canting of the part to be moved. Dividing the traction transfer means into two branches provides sections of the traction transfer means of equal length extending to the entrainment element in each branch, which makes any offset of the entrainment elements impossible. The expense for the further winding drum is not particularly great because it is moved by the same drive as the drive for the existing winding drums.
The invention provides a drive device that prevents the part to be moved from shifting into a canted position. This allows manufacturing tolerances of the components used in the invention to be larger, resulting in increased cost-effectiveness of the device.